JP2011241700A - Bearing structure of camshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent displacement of a bearing structure of a camshaft.SOLUTION: In a cylinder head 10, a hole 34 for positioning is formed on the upper surface 14a of a cam housing 14 to be abutted on a cam cap 12 and another hole 44 for positioning is formed on the lower surface 12b of the cam cap 12 to be abutted on the cam housing 14. When the cam cap 12 and the cam housing 14 are positioned by using a knock pin 30, the lower part 32 of the knock pin 30 is press-fit into the hole 34 and the upper part 42 of the knock pin 30 is press-fit into the hole 44. As a result, the cam cap 12 and the cam housing 14 are positioned so as not to be moved with the knock pin 30 interposed between them and the displacement between the cam cap 12 and the cam housing 14 can be prevented.

Description

  The present invention relates to a camshaft bearing structure, and more particularly to a technique for positioning a camshaft bearing structure using a knock pin.

  Conventionally, a cylinder head provided with a cam cap (cam bracket) and a cam housing (cam carrier) is known (for example, Patent Document 1). The cylinder head is placed on a cylinder block, and a journal hole for rotatably supporting the camshaft is formed. The journal hole may be disposed across the boundary between the cam cap and the cam housing. In such a cylinder head, when the journal hole is formed, the journal hole may be co-processed with the cam cap and the cam housing fastened with a bolt or the like. By doing so, it can be said that the journal hole can be formed more accurately than when the journal hole is separately machined in the cam cap and the cam housing.

Japanese Patent Laid-Open No. 11-247710

  When assembling the camshaft to the cylinder head, the cam cap is removed from the cam housing and the camshaft is mounted on the cam housing, even if journal holes are co-machined in the cam housing and cam cap. Must be attached to the cam housing again and fastened with bolts or the like.

  However, as shown in FIG. 1, the through-hole 46 through which the bolt 40 and the like for fastening the cam housing 14 and the cam cap 12 are inserted is generally wider than the bolt 40 and the like. Between 12, a gap 48 called “play” is provided. Therefore, even when the journal hole is co-machined in the cam housing and cam cap, when the cam cap is re-installed in the cam housing, the cam housing and the cam cap may be displaced by their “play”. It cannot be positioned accurately. By providing a hole for inserting a knock pin in the cam housing and the cam cap, and positioning the cam housing and the cam cap using the knock pin, it is possible to suppress the positional deviation of the journal hole. However, as shown in FIG. 7, in the conventional technique, the knock pin 50 is press-fitted into one side 54 (here, the cam housing side), while the other side 52 (here, the cam cap side) is pressed. There is a gap between them. That is, a gap 56 is provided between the knock pin 50 and the other side 52, and it has not been possible to suppress a positional shift by this gap 56.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a technique capable of preventing displacement of the camshaft bearing structure.

The present invention relates to a bearing structure for a camshaft configured by positioning a first bearing member (example: cam housing) and a second bearing member (example: cam cap) using a knock pin.
In this camshaft bearing structure, a first hole is formed in a surface of the first bearing member that contacts the second bearing member. Moreover, the 2nd hole is formed in the surface contact | abutted to the 1st bearing member of a 2nd bearing member. The first part on one end side of the knock pin is press-fitted into the first hole, and the second part on the other end side of the knock pin is press-fitted into the second hole.

  In the present invention, the knock pin is press-fitted into both the first hole of the first bearing member and the second hole of the second bearing member. Therefore, the first bearing member and the second bearing member can be positioned so as to be immovable via the knock pin, and the positional deviation between the first bearing member and the second bearing member can be reliably prevented.

  In the present invention, the knock pin is press-fitted into both the first bearing member and the second bearing member. For this reason, when the first bearing member is removed from the second bearing member when the camshaft is assembled to the camshaft bearing structure or the like, whether the knock pin is pressed into the first bearing member or the second bearing member. It becomes unknown. For example, when the second bearing member is attached from the upper side to the first bearing member that is mounted and fixed to the lower side when the knock pin is press-fitted into the second bearing member, the first bearing member is provided. The second bearing member is positioned with reference to the hole, and the working efficiency when attaching the first bearing member and the second bearing member is lower than when positioning with the knock pin as a reference.

  In the present invention, the first pulling force required to pull out the first part from the first hole is set larger than the second pulling force required to pull out the second part from the second hole. Therefore, when the second bearing member is removed from the first bearing member, the knock pin can be separated from the second bearing member and press-fitted into the first bearing member. Accordingly, it is possible to prevent the positional deviation between the first bearing member and the second bearing member, improve the reassembling property, and improve the working efficiency when attaching the first bearing member and the second bearing member. it can.

  The press-fitting allowance between the first part and the first hole is preferably larger than the press-fitting allowance between the second part and the second hole. Here, the “press fitting allowance” means a portion where the bearing member and the knock pin interfere with each other. If there is a press-fitting allowance between the knock pin and the hole, when the knock pin is press-fitted into the hole, the hole or the knock pin is elastically deformed, and as a result, a frictional force acts between the hole and the knock pin. Therefore, as the press-fitting allowance increases, the frictional force acting between the hole and the knock pin increases, and the pulling force required to pull out the knock pin from the hole increases. In the present invention, the camshaft in which the first pulling force is larger than the second pulling force by making the press-fitting allowance between the first part and the first hole larger than the press-fitting allowance between the second part and the second hole. The bearing structure can be realized.

  The first minor angle between the axial direction of the first part and the surface direction of the side surface of the first hole is preferably larger than the second minor angle between the axial direction of the second part and the surface direction of the side surface of the second hole. Here, the “subordinate angle” means a small angle among the angles formed by the two directions in a plane specified by the two directions.

  Normally, the knock pin is pressed in the axial direction and inserted into the hole. That is, the axial direction of the knock pin is equal to the direction in which the knock pin is press-fitted into the corresponding hole, and is equal to the direction in which the knock pin is pulled out from the hole. Also, the frictional force acting between the hole and the knock pin acts in a direction perpendicular to the surface direction of the side surface of the hole, and if the direction in which the knock pin is pulled out from the hole and the direction in which the frictional force does not match, the knock pin is removed from the hole. A component of frictional force acts in the pulling direction. The component force of the frictional force acting in the direction of pulling out the knock pin from the hole (that is, the axial direction of the knock pin) increases as the angle between the direction of pulling out the knock pin from the hole and the surface direction of the side surface of the hole increases. That is, it increases as the recess angle between the axial direction of the knock pin and the surface direction of the side surface of the hole increases.

  According to the above configuration, even when the friction force acting between the first part and the first hole is equal to the friction force acting between the second part and the second hole, the friction force acting in the first direction is reduced. The frictional force acting in the second direction can be made larger. Thus, it is possible to realize a camshaft bearing structure in which the first pulling force is larger than the second pulling force.

  Preferably, the first hole has a columnar shape in the first direction, and the second hole has a taper shape in the second direction. When the second hole has a tapered shape with respect to the second direction, the first bearing member and the second bearing member can be positioned by inserting the second portion into the second hole. And the working efficiency at the time of attaching a 2nd bearing member can be improved. Further, when the first hole has a cylindrical shape with respect to the first direction and the second hole has a tapered shape with respect to the second direction, the first minor angle is made larger than the second minor angle. Therefore, it is possible to realize a camshaft bearing structure in which the first pulling force is larger than the second pulling force.

  When the first bearing member is composed of the first member, the second bearing member is composed of the second member, and the knock pin is composed of the third member, the first member and the second member are different. The friction coefficient between the first member and the third member is preferably larger than the friction coefficient between the second member and the third member. Thereby, the frictional force acting between the first part and the first hole can be made larger than the frictional force acting between the second part and the second hole, and the first pulling force is greater than the second pulling force. A large camshaft bearing structure can be realized.

  Conventionally, the first bearing member and the second bearing member are fastened with a fastener (bolt or the like). In this case, it is preferable that the pressure input required to press-fit the second part into the second hole is smaller than the fastening force of the fastener. Thus, even when the knock pin is press-fitted into the second bearing member, the second portion can be press-fitted into the second hole by using a force acting on the first bearing member and the second bearing member when fastening the fastener. It is possible to prevent the work efficiency from deteriorating.

  According to the present invention, it is possible to prevent displacement of the camshaft bearing structure.

Cross section of cylinder head 10 The figure which shows the relationship between the lower part 32 and the hole 34 of the knock pin 30, and the relationship between the upper part 42 and the hole 44 of the knock pin 30 Cross section of cylinder head 110 Cross section of knock pin 130 Expanded sectional view of knock pin 130 Sectional view of cylinder head 210 The figure explaining positioning using the conventional knock pin

<Embodiment 1>
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, in an engine mounted on a vehicle, a cylinder head 10 (bearing structure of a camshaft) is provided on a top surface side of a cylinder block (not shown) on which a cylinder is arranged via a head gasket (not shown). Example) is fixed. The cylinder head 10 includes a cam cap 12 (an example of a second bearing member) and a cam housing 14 (an example of a first bearing member). The cam cap 12 and the cam housing 14 are made of the same member such as an aluminum alloy. The cam housing 14 accommodates a valve 20 such as an intake valve for sucking a mixed gas of fuel and oxygen into the cylinder and an exhaust valve for exhausting the combustion gas combusted by the mixed gas from the cylinder. A journal hole 28 is formed at the boundary 16 between the cam cap 12 and the cam housing 14 to rotatably support the camshaft 24 that determines the opening / closing timing of the valve 20.

  A through hole 46 is formed in the cam cap 12 so as to penetrate from the upper surface 12 a to the lower surface 12 b in contact with the cam housing 14. Further, a fastening hole 36 that is screwed with the bolt 40 is formed at a position corresponding to the through hole 46 of the upper surface 14 a that contacts the cam cap 12 of the cam housing 14. The diameter of the through hole 46 is larger than the diameter of the bolt 40, and the diameter of the fastening hole 36 is equal to the diameter of the bolt 40. When the cam cap 12 and the cam housing 14 are fastened, the bolt 40 is passed through the through hole 46 and the bolt 40 and the fastening hole 36 are screwed together. A gap 48 is provided between the bolt 40 and the cam cap 12. Therefore, when the cam cap 12 and the cam housing 14 are positioned using the bolt 40, the cam housing 14 and the cam cap 12 are positioned so as to be movable by the gap 48 between the bolt 40 and the through hole 46.

  A cylindrical hole 44 (corresponding to the second hole) for inserting the upper part 42 (corresponding to the second part) of the cylindrical knock pin 30 is formed in the lower surface 12b of the cam cap 12. The depth of the hole 44 is set to be equal to or higher than the height of the upper portion 42. As shown in FIG. 2, the diameter φ1 of the hole 44 is set smaller than the diameter φ2 of the upper portion 42. That is, a press-fitting allowance S1 (= φ2−φ1) is formed between the hole 44 and the upper portion 42. In FIG. 2, the press-fitting allowance S <b> 1 is shown thick for explanation. Therefore, when the upper part 42 is inserted into the hole 44, the upper part 42 is press-fitted into the hole 44, and the knock pin 30 is fixed to the cam cap 12 so as not to move. The thickness of the press-fit allowance S1 is about 10 μm, and the press-fit allowance of the embodiment shown below is also about the same.

  A cylindrical hole 34 (corresponding to the first hole) for inserting the lower portion 32 (corresponding to the first part) of the cylindrical knock pin 30 is formed at a position corresponding to the hole 44 on the upper surface 14a of the cam housing 14. Has been. The depth of the hole 34 is equal to the height of the lower portion 32 and equal to the height of the upper portion 42. As shown in FIG. 2, the diameter φ3 of the hole 34 is set smaller than the diameter φ4 of the lower portion 32. That is, a press-fitting allowance S2 (= φ4-φ3) is formed between the hole 34 and the lower portion 32. Therefore, when the lower portion 32 is inserted into the hole 34, the lower portion 32 is press-fitted into the hole 34, and the knock pin 30 is fixed to the cam housing 14 so as not to move.

  In this embodiment, the knock pin 30 is fixed to the cam cap 12 so as not to move, and the knock pin 30 is fixed to the cam housing 14 so as not to move. Therefore, the cam cap 12 and the cam housing 14 are positioned so as not to move via the knock pin 30. As a result, it is possible to reliably prevent displacement between the cam cap 12 and the cam housing 14. For example, even when the journal hole 28 is co-machined in the cam cap 12 and the cam housing 14, the cam cap 12 is removed from the cam housing 14, and the cam cap 12 is attached to the cam housing 14 again, the journal hole is accurately reproduced. can do.

  In this embodiment, the press-fit allowance S2 between the hole 34 and the lower portion 32 of the knock pin 30 is set to be larger than the press-fit allowance S1 between the hole 44 and the upper portion 42 of the knock pin 30. Therefore, the frictional force acting between the hole 34 and the lower part 32 can be made larger than the frictional force acting between the hole 44 and the upper part 42. That is, the force F1 (corresponding to the first pulling force) required to pull out the lower portion 32 of the knock pin 30 from the hole 34, and the force F2 (second pulling force) required to pull out the upper portion 42 of the knock pin 30 from the hole 44. Equivalent). As a result, even when the cam cap 12 and the cam housing 14 once attached are removed, the knock pin 30 can be detached from the cam cap 12 and press-fitted into the cam housing 14. When the cam cap 12 is attached to the cam housing 14 again after the camshaft 24 is received, the cam cap 12 can be positioned with reference to the knock pin 30 protruding from the upper surface 14a of the cam housing 14, and the cam cap 12 can be positioned in the cam housing. The work efficiency at the time of attaching to 14 can be improved.

  In the present embodiment, the press-fit allowance S2 between the hole 34 and the lower portion 32 of the knock pin 30 is set to be larger than the press-fit allowance S1 between the hole 44 and the upper portion 42 of the knock pin 30. The force required to press-fit the lower portion 32 of the pin 30 into the hole 34 is set to be larger than the force required to press-fit the upper portion 42 of the knock pin 30 into the hole 44. In the present embodiment, the force required to press-fit the upper portion 42 of the knock pin 30 into the hole 44 is set to be smaller than the coupling force required to screw the bolt 40 into the fastening hole 36. Yes. Therefore, when the cam cap 12 is placed so that the hole 44 is disposed immediately above the knock pin 30 and the bolt 40 is screwed into the fastening hole 36 through the through hole 46, the cam cap 12 is coupled to the cam housing 14. At the same time, the upper portion 42 of the knock pin 30 is press-fitted into the hole 44 by a fastening force for screwing the bolt 40, and the cam cap 12 and the cam housing 14 are positioned. Thereby, even when the upper part 42 of the knock pin 30 is press-fitted into the hole 44, the upper part 42 of the knock pin 30 can be press-fitted into the hole 44 simultaneously with the conventional fastening process of the cam cap 12 and the cam housing 14. It is possible to prevent work efficiency from deteriorating due to an increase in work processes.

<Embodiment 2>
FIG. 3 shows the structure of the second embodiment of the present invention. In the cylinder head 110 according to the present embodiment, the shapes of the upper portion 142 and the hole 144 of the knock pin 130 are changed as compared with the cylinder head 10 according to the first embodiment, and redundant description of other structures is omitted.

  As shown in FIG. 4 in an enlarged manner, the upper portion 142 of the knock pin 130 has a conical shape (tapered shape), and the lower portion 32 of the knock pin 130 has a cylindrical shape. The axis 142 of the upper part 142 and the lower part 32 coincides. The diameter of the lowermost part of the upper part 142 is set to be equal to the diameter of the lower part 32, and the upper part 142 and the lower part 32 are continuous in diameter at the connection part. A side surface of the conical upper portion 142 forms an angle of θ1 (0 <θ1 <π) with the axis Z. On the other hand, the side surface of the cylindrical upper portion 142 extends parallel to the axis Z.

  A conical hole 144 (corresponding to the second hole) for inserting the conical upper part 142 is formed in the lower surface 112b of the cam cap 112. The depth of the hole 144 is equal to the height of the upper part 142 and equal to the height of the hole 34 provided in the lower part 32 and the cam housing 14. The diameter of the cross section at an arbitrary depth of the hole 144 is set smaller than the diameter of the cross section at the corresponding height of the upper portion 142. That is, a press-fitting allowance is formed between the hole 144 and the upper part 142. Therefore, when the upper portion 142 is inserted into the hole 144, the upper portion 142 is press-fitted into the hole 144, and the knock pin 30 is fixed to the cam cap 112 so as not to move.

The knock pin 130 is pressed into the hole 144 by pressing the upper portion 142 in the direction of the axis Z, and is pressed into the hole 34 by pressing the lower portion 32 in the direction of the axis Z. As shown in FIG. 4, the axis Z is in the vertical direction in a state where the upper portion 142 is press-fitted into the hole 144 and the lower portion 32 is press-fitted into the hole 34. That is, the axial direction of the upper part 142 and the direction of the axis Z of the lower part 32 are both vertical directions. Therefore, when the upper portion 142 is pulled out from the hole 144, the upper portion 142 is pulled vertically downward, and when the lower portion 32 is pulled out from the hole 34, the lower portion 32 is pulled vertically upward.
In the present embodiment, the cam cap 112 and the cam housing 14 are composed of the same member. The press-fitting allowance between the hole 34 and the lower part 32 of the knock pin 130 is set to be equal to or greater than the press-fitting allowance between the hole 144 and the upper part 142 of the knock pin 130.

  In this embodiment, the upper part 142 and the hole 144 have a conical shape. Therefore, when the upper part 142 is inserted into the hole 144, the hole 144 and the upper part 142 can be positioned by moving relative to each other along the conical side surfaces. Thereby, the working efficiency when the cam cap 112 is attached to the cam housing 14 can be improved.

  In the present embodiment, the lower portion 32 and the hole 34 are cylindrical. Therefore, as shown in FIG. 5 in which the dotted line portion V of FIG. 4 is enlarged, the direction D1 (the vertical direction and corresponding to the axial direction of the first portion) that pulls out the lower portion 32 from the hole 34 is along the side surface of the hole 34. Which is perpendicular to the surface direction H1 of the side surface of the hole 34 (that is, the first minor angle = 90 degrees). As a result, the frictional force M1 between the lower portion 32 and the hole 34 acts in the same straight line as the direction D1, and the direction is reversed. That is, the force F1 required to pull out the lower portion 32 of the knock pin 130 from the hole 34 needs to be larger than the frictional force M1.

  On the other hand, the upper part 142 and the hole 144 are conical. Therefore, as shown in FIG. 5, the direction D2 (the vertical direction and corresponding to the axial direction of the second portion) in which the upper portion 142 is pulled out from the hole 144 does not coincide with the direction along the side surface of the hole 144. A predetermined acute angle θ2 (corresponding to the second subordinate angle: θ2 = π−θ1) is formed between the side surface and the surface direction H2. As a result, the frictional force M2 between the upper portion 142 and the hole 144 does not act in the same straight line as the direction D2, and the component force Mb2 of the frictional force M2 acts in the opposite direction of the direction D2. That is, the force F2 required to pull out the upper portion 142 of the knock pin 130 from the hole 144 only needs to be larger than the component force Mb1 of the frictional force M1.

  In this embodiment, even when the frictional force M1 and the frictional force M2 are equal, the force F1 required to pull out the lower part 32 of the knock pin 30 from the hole 34 is used to pull out the upper part 142 of the knock pin 30 from the hole 144. It can be made larger than the necessary force F2. As a result, as in the first embodiment, the working efficiency when the cam cap 112 is attached to the cam housing 14 can be improved.

<Other embodiments>
The present invention is not limited to the embodiments described above with reference to the drawings and can be applied to the following embodiments, for example.
(1) In the above embodiment, the description has been made assuming that the materials of the cam cap 12 and the cam housing 14 are the same. However, the cam cap 12 and the cam housing 14 may be composed of different members. In this case, these members have a coefficient of friction between the member used for the cam cap 12 and the member used for the knock pin 30 between the single member constituting the upper part 42 and the lower part 32 of the knock pin 30. The friction coefficient between the member used for the housing 14 and the member used for the knock pin 30 is preferably selected to be larger. As a result, the frictional force acting between the hole 34 and the lower part 32 can be made larger than the frictional force acting between the hole 44 and the upper part 42, which is necessary for pulling out the lower part 32 of the knock pin 30 from the hole 34. The force F1 can be made larger than the force F2 required to pull out the upper part 42 of the knock pin 30 from the hole 44. As in the first and second embodiments, the working efficiency when the cam cap 12 is attached to the cam housing 14 can be improved.

(2) In the above embodiment, the depth of the hole 44 formed in the cam cap 12 and the depth of the hole 34 formed in the cam housing 14 are described as being the same. However, the depth of the hole 44 and the hole 34 are described. The depth of the may be different. In this case, the depth of the hole 34 is preferably set deeper than the depth of the hole 44. The frictional force acting between the hole and the knock pin 30 is proportional to its surface area. By setting as described above, the frictional force acting between the hole 34 and the lower part 32 can be made larger than the frictional force acting between the hole 44 and the upper part 42, and the lower part 32 of the knock pin 30 can be The force F1 required to pull out from the hole 34 can be made larger than the force F2 required to pull out the upper portion 42 of the knock pin 30 from the hole 44. As in the first and second embodiments, the working efficiency when the cam cap 12 is attached to the cam housing 14 can be improved.

(3) In the above embodiment, an example using the cylindrical or conical knock pins 30 and 130 has been shown, but the shape of the knock pins 30 and 130 is not limited thereto. Like the cylinder head 210 shown in FIG. 6, the knock pin 230 may have a cylindrical shape, and the bolt 40 may be disposed so as to penetrate the through hole 260 formed in the knock pin 230. A gap 262 is formed between the bolt 40 and the knock pin 230. On the other hand, the knock pin 230 is press-fitted into the cam housing 214 and press-fitted into the cam cap 212. Accordingly, even in the case of the knock pin 230 having the shape shown in FIG. 6, it is possible to reliably prevent the displacement between the cam cap 212 and the cam housing 214.

(4) In the above embodiment, the press-fitting allowance S is described as the difference between the hole diameter φ5 and the knock pin diameter φ6 (S = φ6-φ5), but may be a quotient (S = φ5 / φ6). Thereby, the value of the press-fit allowance S according to the diameter φ6 of the knock pin can be set.

(5) In the above embodiment, the first bearing member has been described as a cam housing and the second bearing member as a cam cap. However, the first bearing member and the second bearing member are not limited thereto. For example, when the camshaft is pivotally supported by a cylinder head and a cam cap, the first bearing member is a cylinder head. When the camshaft is pivotally supported by a bearing member different from the cylinder head and the cam cap, the second bearing member is the bearing member.

10: Cylinder head 12: Cam cap 14: Cam housing 24: Cam shaft 28: Journal hole 30: Knock pin 32: Lower part (first part)
34: Hole (first hole)
40: Bolt 42: Upper part (second part)
44: Hole (second hole)

Claims (7)

A camshaft bearing structure configured by positioning a first bearing member and a second bearing member using a knock pin,
A first hole is formed in a surface of the first bearing member that contacts the second bearing member,
A second hole is formed in a surface of the second bearing member that contacts the first bearing member,
The first part on one end side of the knock pin is press-fitted into the first hole,
The second part on the other end side of the knock pin is a camshaft bearing structure that is press-fitted into the second hole. The camshaft bearing structure according to claim 1,
A camshaft bearing structure in which a first pulling force required to pull out the first part from the first hole is greater than a second pulling force required to pull out the second part from the second hole. The camshaft bearing structure according to claim 2,
A camshaft bearing structure in which a press-fitting allowance between the first part and the first hole is larger than a press-fitting allowance between the second part and the second hole. The camshaft bearing structure according to claim 2 or 3,
The first minor angle between the axial direction of the first part and the surface direction of the side surface of the first hole is larger than the second minor angle between the axial direction of the second part and the surface direction of the side surface of the second hole. Camshaft bearing structure. The camshaft bearing structure according to claim 4,
The first hole has a cylindrical shape in the first direction,
The bearing structure of the camshaft in which the second hole is tapered in the second direction. The camshaft bearing structure according to any one of claims 2 to 5,
The first bearing member comprises a first member;
The second bearing member comprises a second member;
The knock pin is composed of a third member,
The first member and the second member are different,
A camshaft bearing structure in which a friction coefficient between the first member and the third member is larger than a friction coefficient between the second member and the third member. The camshaft bearing structure according to any one of claims 2 to 6,
The first bearing member and the second bearing member are fastened by a fastener,
A camshaft bearing structure in which a pressure input required to press-fit the second portion into the second hole is smaller than a fastening force of the fastener.

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